Liquid ejection head

ABSTRACT

A liquid ejection head, comprises a pressure generation chamber communicating with a nozzle opening and a piezoelectric element having a piezoelectric layer and an electrodes. The piezoelectric layer is a perovskite type complex oxide containing bismuth, iron, and cerium. The piezoelectric layer contains the cerium in a proportion of 0.01 molar ratio or more and 0.13 molar ratio or lower based on the total amount of the bismuth and the cerium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/046,671 filed on Mar. 11, 2011, which claims the benefit of priorityto Japanese Patent Application No. 2010-056806 filed Mar. 12, 2010, andJapanese Patent Application No. 2010-122800 filed May 28, 2010, thecontents of which are hereby incorporated by reference in theirentireties.

BACKGROUND

1. Technical Field

The present invention relates to a liquid ejection head having apiezoelectric element that causes a pressure change in a pressuregenerating chamber communicating with a nozzle opening and has apiezoelectric layer and an electrode for applying a voltage to thepiezoelectric layer, a liquid ejection device, a piezoelectric element,and a piezoelectric material.

2. Related Art

Mentioned as piezoelectric elements for use in liquid ejection heads isa piezoelectric element having a structure where a piezoelectricmaterial that exhibits an electromechanically conversion function, suchas a piezoelectric layer containing a crystallized dielectric material,is sandwiched between two electrodes. Such a piezoelectric element ismounted on a liquid ejection head as, for example, an actuator device ina bending vibration mode. Mentioned as a typical example of the liquidejection head is, for example, an ink jet recording head in which a partof a pressure generation chamber communicating with a nozzle opening fordischarging ink droplets is constituted by a diaphragm and whichdischarges ink in the pressure generation chamber as ink droplets fromthe nozzle opening by deforming the diaphragm by the piezoelectricelement to pressurize the ink. Mentioned as the piezoelectric element tobe mounted on such an ink jet recording head is, for example, apiezoelectric element formed by forming a uniform piezoelectric materiallayer throughout the entire surface of the diaphragm by a film formationtechnique, and then cutting the piezoelectric material layer into ashape corresponding to the pressure generation chamber by a lithographymethod to be independent for every pressure generation chamber.

The piezoelectric material for use in such a piezoelectric element isrequired to have high piezoelectric characteristics (distortion level),and lead zirconate titanate (PZT) is mentioned as a typical example(JP-A-2001-223404).

However, a piezoelectric material in which the lead content is reducedhas been desired from the viewpoint of environmental problems. Examplesof piezoelectric materials not containing lead include BiFeO₃ which is aperovskite type complex oxide represented by, for example, ABO₃. Such aBiFeO₃-based piezoelectric material containing Bi and Fe has problems inthat the insulation properties are low and a leakage current occurs.Such problems similarly occur in other piezoelectric elements withoutbeing limited to the liquid ejection head typified by the ink jetrecording head.

SUMMARY

An advantage of some aspects of the invention is to provide a liquidejection head having a piezoelectric element that has high insulationproperties, can suppress the generation of a leakage current, and has areduced environmental load, a liquid ejection device, a piezoelectricelement, and a piezoelectric material.

According to a first aspect of the invention that solves theabove-described problems is a liquid ejection head having a pressuregeneration chamber communicating with a nozzle opening and apiezoelectric element having a piezoelectric layer and an electrodeprovided on the piezoelectric layer, in which the piezoelectric layer isa perovskite type complex oxide containing bismuth, iron, and cerium andthe piezoelectric layer contains the cerium in a proportion of 0.01 ormore and 0.13 or lower in a molar ratio based on the total amount of thebismuth and the cerium.

According to such an aspect, by the use of the piezoelectric materialcontaining a perovskite type complex oxide containing iron and bismuthand a given proportion of cerium for the piezoelectric layer, highinsulation properties can be obtained and the generation of a leakagecurrent can be suppressed. Moreover, since the lead content can bereduced, a load to the environment can be reduced.

The piezoelectric layer may further contain lanthanum. According to thisaspect, a liquid ejection head having a piezoelectric material that canbecome a ferroelectric or an antiferroelectric exhibiting an electricfield-induced phase transition while maintaining the effects ofobtaining high insulation properties and suppressing the generation of aleakage current is obtained. Moreover, a hetero-phase derived frombismuth ferrate can be suppressed.

The piezoelectric layer contains the lanthanum in a proportion of 0.05or more and 0.20 or lower in a molar ratio based on the total amount ofthe bismuth, the cerium, and the lanthanum. According to this aspect, aliquid ejection head having a piezoelectric material of a ferroelectricor an antiferroelectric exhibiting an electric field-induced phasetransition in accordance with the lanthanum amount is achieved.

The piezoelectric layer may exhibit an electric field-induced phasetransition. According to this aspect, a liquid ejection head having apiezoelectric element having a high distortion level can be achieved.

The piezoelectric layer may be a ferroelectric. According to thisaspect, a liquid ejection head having a piezoelectric element in whichthe distortion level is easily controlled, and, for example, the size ofdroplets to be discharged is easily controlled can be achieved.

It is preferable that, in the piezoelectric layer, a diffraction peakbelonging to a phase exhibiting ferroelectricity and a diffraction peakbelonging to a phase exhibiting antiferroelectricity be simultaneouslyobserved in a powder X-ray diffraction pattern. According to thisaspect, a piezoelectric element having a high distortion level can beobtained due to the presence of a Morphotropic phase boundary (M. P. B.)of an antiferroelectric phase and a ferroelectric phase.

According to a seventh aspect, a liquid ejection device has the liquidejection head of the aspects described above. According to such anaspect, a liquid ejection device in which dielectric breakdown isprevented and the reliability is excellent is obtained because theliquid ejection device has a liquid ejection head having high insulationproperties and capable of suppressing the generation of a leakagecurrent. In addition, a liquid ejection device in which the lead contentis reduced and a load to the environment is reduced can be provided.

According to an eighth aspect of the invention, a piezoelectric elementhas a piezoelectric layer and an electrode provided on the piezoelectriclayer, in which the piezoelectric layer is a perovskite type complexoxide containing bismuth, iron, and cerium and the piezoelectric layercontains the cerium in a proportion of 0.01 or more and 0.13 or lower ina molar ratio based on the total amount of the bismuth and the cerium.According to the aspect, high insulation properties can be obtained andthe generation of a leakage current can be suppressed by the use of apiezoelectric material containing a perovskite type complex oxidecontaining iron and bismuth and a given ratio of cerium for thepiezoelectric layer. Moreover, since the lead content can be reduced, aload to the environment can be reduced.

According to a ninth aspect of the invention, a piezoelectric materialwhich is a perovskite type complex oxide containing bismuth, iron, andcerium and which contains the cerium in a proportion of 0.01 or more and0.13 or lower in a molar ratio based on the total amount of the bismuthand the cerium. According to the aspect, a piezoelectric material inwhich the insulation properties are high and the generation of a leakagecurrent can be suppressed is obtained. Moreover, since the lead contentcan be reduced, a load to the environment can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is an exploded perspective view schematically illustrating thestructure of a recording head according to a first embodiment.

FIG. 2 is a plan view of the recording head according to the firstembodiment.

FIG. 3 is a cross sectional view of the recording head according to thefirst embodiment.

FIG. 4 is a diagram illustrating the P-V hysteresis of anantiferroelectric.

FIGS. 5A and 5B are cross sectional views illustrating a process formanufacturing the recording head according to the first embodiment.

FIGS. 6A to 6C are cross sectional views illustrating the process formanufacturing the recording head according to the first embodiment.

FIGS. 7A and 7B are cross sectional views illustrating the process formanufacturing the recording head according to the first embodiment.

FIGS. 8A to 8C are cross sectional views illustrating the process formanufacturing the recording head according to the first embodiment.

FIGS. 9A and 9B are cross sectional views illustrating the process formanufacturing the recording head according to the first embodiment.

FIGS. 10A to 10D are views illustrating the P-E curve of samples 1 to 4.

FIG. 11 is a diagram illustrating the X ray diffraction pattern of thesamples 1 to 4.

FIG. 12 is a diagram illustrating the J-E Curve of the samples 1 to 4.

FIG. 13 is a diagram illustrating the S-V curve of the sample 1.

FIGS. 14A to 14D are diagrams illustrating the P-E curve of the samples6, 11, 17, and 21.

FIG. 15 is a diagram illustrating the X ray diffraction pattern of thesamples 2 and 11.

FIGS. 16A and 16B are diagrams illustrating the X ray diffractionpattern of the samples 6, 11, and 17.

FIG. 17 is a diagram in which the analysis results of the X raydiffraction pattern are plotted against the composition.

FIGS. 18A to 18B are diagram s illustrating the measurement results ofthe J-E Curve.

FIGS. 19A to 19D are diagram s illustrating the S-V curve of the samples6, 11, 17, and 21.

FIG. 20 is a view schematically illustrating the structure of arecording device according to one embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

FIG. 1 is an exploded perspective view schematically illustrating thestructure of an ink jet recording head which is one example of a liquidejection head according to a first embodiment of the invention, FIG. 2is a plan view of FIG. 1, and FIG. 3 is a cross sectional view along theIII-III line of FIG. 2. As illustrated in FIGS. 1 to 3, a flow pathforming substrate 10 of this embodiment contains a silicon singlecrystal substrate, on one surface of which an elastic film 50 containingsilicon dioxides is formed.

In the flow path forming substrate 10, two or more pressure generationchambers 12 are arranged in parallel in the width direction thereof. Inan outside region in the longitudinal direction of the pressuregeneration chambers 12 of the flow path forming substrate 10, acommunication portion 13 is formed and the communication portion 13 andeach pressure generation chamber 12 are communicated with each otherthrough an ink supply path 14 and a communication path 15 provided forevery pressure generation chamber 12. The communication portion 13communicates with a reservoir portion 31 of a protective substratedescribed later to constitute a part of a reservoir to serve as a commonink chamber of the respective pressure generation chambers 12. The inksupply path 14 is formed with a narrower width than that of the pressuregeneration chamber 12 and keeps the flow path resistance of ink flowinginto the pressure generation chamber 12 from the communication portion13 at a constant rate. In this embodiment, the ink supply path 14 isformed by narrowing the width of the flow path from one side but the inksupply path may be formed by narrowing the width of the flow path fromboth sides. The ink supply path may be formed by narrowing in thethickness direction instead of narrowing the width of the flow path. Inthis embodiment, the flow path forming substrate 10 is provided with aliquid flow path constituted by the pressure generation chambers 12, thecommunication portion 13, the ink supply paths 14, and the communicationpaths 15.

To the opening surface side of the flow path forming substrate 10, anozzle plate 20 in which nozzle openings 21 each communicating with thevicinity of the end of each pressure generation chamber 12 opposite tothe ink supply paths 14 are formed is adhered with an adhesive, athermally welding film, or the like. The nozzle plate 20 contains glassceramics, a silicon single crystal substrate, stainless steel, or thelike, for example.

In contrast, on the side opposite to the opening surface of such a flowpath forming substrate 10, the elastic film 50 is formed as describedabove. On the elastic film 50, an adhesion layer 56 containing titaniumoxide for increasing the adhesion of the elastic film 50 or the likewith the base of a first electrode 60 is provided. On the elastic film50, an insulator film containing zirconium dioxide or the like may beprovided as required.

Furthermore, on the adhesion layer 56, the first electrode 60, apiezoelectric layer 70 which is a thin film having a thickness of 2 μmor lower and preferably 1 to 0.3 μm, and a second electrode 80 arelaminated to constitute a piezoelectric element 300. Here, thepiezoelectric element 300 refers to a portion containing the firstelectrode 60, the piezoelectric layer 70, and the second electrode 80.In general, any one of the electrodes of the piezoelectric elements 300is used as a common electrode and the other electrodes and thepiezoelectric layers 70 are formed by patterning for every pressuregeneration chamber 12. In this embodiment, the first electrode 60 isused as the common electrode of the piezoelectric elements 300 and thesecond electrode 80 is used as an individual electrode of thepiezoelectric elements 300 but the electrodes may be used in an oppositemanner depending on a drive circuit or wiring. Here, a combination ofthe piezoelectric element 300 and a diaphragm in which displacementarises by the drive of the piezoelectric element 300 is referred to asan actuator device. In the above-described example, the elastic film 50,the adhesion layer 56, the first electrode 60, and the insulator filmprovided as required act as the diaphragm. However, it is a matter offact that the invention is not limited to the example and the elasticfilm 50 or the adhesion layer 56 may not be provided, for example. Thepiezoelectric element 300 may substantially serve as the diaphragm.

In this embodiment, a piezoelectric material constituting thepiezoelectric layer 70 is a perovskite type complex oxide containingbismuth, iron, and cerium. On the A site of the perovskite type complexoxide, i.e., an ABO₃ type complex oxide, twelve oxygens are coordinatedand, on the B site, six oxygens are coordinated to form an octahedron.On the A site, bismuth (Bi) and cerium (Ce) are positioned and, on the Bsite, iron (Fe) is positioned. More specifically, the perovskite typecomplex oxide containing bismuth, iron, and cerium is presumed to have astructure where a part of Bi of bismuth ferrate is replaced by Ce.

In this embodiment, in the perovskite type complex oxide containingbismuth, iron, and cerium, Ce is contained in a proportion of 0.01 ormore and 0.13 or lower in a molar ratio based on the total amount of Biand Ce.

Thus, when the perovskite type complex oxide containing bismuth, iron,and cerium is used as the piezoelectric material constituting thepiezoelectric layer 70 and the proportion of the cerium is adjusted tobe 0.01 or more and 0.13 or lower in a molar ratio based on the totalamount of the bismuth and the cerium, the insulation properties can bemade high and a leakage current can be suppressed as compared with apiezoelectric material not containing Ce, i.e., a BiFeO₃ typepiezoelectric material containing Bi and Fe and not containing Ce asshown in Examples described later. It is a matter of course that sincethe lead content can be reduced, a load to the environment can bereduced. For example, the piezoelectric layer 70 in which a leakagecurrent when a 500 kVcm⁻¹ electric field is applied is equal to or lowerthan 1.0×10⁻¹ Acm⁻² can be achieved.

The piezoelectric layer 70 may further contain lanthanum (La). By theuse of a perovskite type complex oxide containing bismuth, iron, cerium,and lanthanum, a piezoelectric material that can become a ferroelectricor an antiferroelectric exhibiting an electric field-induced phasetransition. The perovskite type complex oxide containing bismuth, iron,cerium, and lanthanum is presumed to have a structure where a part of Biof bismuth ferrate is replaced by Ce and La.

It is a matter of course that even in the case of a piezoelectricmaterial further containing La, the effects of increasing the insulationproperties to a high degree and suppressing a leakage current can alsobe maintained. The La content is not limited and may be adjusted to be,for example, 0.05 or more and 0.20 or lower in a molar ratio based onthe total amount of Bi, Ce, and La.

Here, the electric field-induced phase transition is a phase transitioncaused by an electric field and refers to a phase transition from anantiferroelectric phase to a ferroelectric phase or a phase transitionfrom a ferroelectric phase to an antiferroelectric phase. Theferroelectric phase refers to a state where the polarization axes areoriented in the same direction and the antiferroelectric phase refers toa state where the polarization axes are oriented in the oppositedirection. For example, the phase transition from an antiferroelectricphase to a ferroelectric phase refers to a state where the polarizationaxes oriented in the opposite direction of the antiferroelectric phaserotate 180°, so that the polarization axes are oriented in the samedirection to convert the phase to a ferroelectric phase. A distortioncaused by expansion or contraction of a lattice due to such an electricfield-induced phase transition is an electric field-induced phasetransition distortion caused by the electric field-induced phasetransition.

A substance exhibiting such an electric field-induced phase transitionis the antiferroelectric. In other words, a substance in which thepolarization axes are oriented in the opposite direction in a statewhere there is no electric field and the polarization axes rotate by anelectric field to be oriented in the same direction is theantiferroelectric. Such an antiferroelectric exhibits a doublehysteresis having two hysteresis loop shapes in a positive electricfield direction and a negative electric field direction as illustratedin FIG. 4 illustrating one example of the P-V curve representing therelationship between the polarization P and the voltage V of theantiferroelectric. In FIG. 4, the regions VF and VAF where thepolarization rapidly changes are portions where the phase transitionfrom the ferroelectric phase to the antiferroelectric phase or the phasetransition from the ferroelectric phase to the antiferroelectric phaseoccurs. Unlike the antiferroelectric, the ferroelectric exhibits ahysteresis curve in the P-V curve, in which the distortion levellinearly changes to an applied voltage by orienting the polarizationdirection to one direction.

In contrast, in the antiferroelectric, the P-V curve does not exhibit adouble hysteresis which is observed in the antiferroelectric and thedistortion level linearly changes to an applied voltage by orienting thepolarization direction to one direction. Thus, since the distortionlevel is easily controlled, the size of droplets to be discharged iseasily controlled, and both a small-amplitude vibration that causes aslight vibration and a large-amplitude vibration that generates a largeexcluded volume can be generated by one piezoelectric element.

In the case of the ferroelectric, when the piezoelectric layer 70 issubjected to powder X-ray diffraction measurement, the diffraction peakbelonging to a phase exhibiting ferroelectricity (ferroelectric phase)is observed in the diffraction pattern. It is preferable that thediffraction peak belonging to the phase exhibiting ferroelectricity(ferroelectric phase) and the diffraction peak belonging to a phaseexhibiting antiferroelectricity (antiferroelectric phase) besimultaneously observed. Thus, in the case of the piezoelectric layer 70in which the diffraction peak belonging to the phase exhibitingferroelectricity and the diffraction peak belonging to the phaseexhibiting antiferroelectricity are simultaneously observed, i.e.,exhibiting the Morphotropic phase boundary (M. P. B.) of theantiferroelectric phase and the ferroelectric phase, a piezoelectricelement having a high distortion level can be achieved amongferroelectrics. The diffraction peak belonging to the phase exhibitingferroelectricity is observed near 2θ=46° when powder X-ray diffractionmeasurement is carried out, for example. The diffraction peak belongingto the phase exhibiting antiferroelectricity is observed near 2θ=46.5°when powder X-ray diffraction measurement using a CuKα line as the X-raysource is carried out, for example. These diffraction peak positions aredependent on planar spacing and a shift in the diffraction peak positionmay occur due to changes in a stress from a substrate or the outsidedepending on a creation method, shape, external stress, or the like. Incontrast, in the antiferroelectric, the diffraction peak belonging tothe phase exhibiting ferroelectricity is not observed and only thediffraction peak belonging to the phase exhibiting antiferroelectricityis observed.

When the piezoelectric layer 70 contains La, a hetero-phase derived frombismuth ferrate can be suppressed.

To each of the second electrodes 80 which are individual electrodes ofsuch piezoelectric elements 300, a lead electrode 90 containing gold(Au) or the like, for example, which is drawn from the vicinity of theend at the ink supply path 14 side to be extended onto the elastic film50 or the insulator film provided as required.

On the flow path forming substrate 10 on which such piezoelectricelements 300 are formed, i.e., on the first electrode 60, the elasticfilm 50, the insulator film provided as required, and the lead electrode90, a protective substrate 30 having the reservoir portion 31constituting at least one part of a reservoir 100 is joined through anadhesive 35. The reservoir portion 31 is formed penetrating theprotective substrate 30 in the thickness direction and in the widthdirection of the pressure generation chamber 12 and is communicated withthe communication portion 13 of the flow path forming substrate 10 asdescribed above to constitute the reservoir 100 to serve as a common inkchamber of the respective pressure generation chambers 12 in thisembodiment. Or, the communication portion 13 of the flow path formingsubstrate 10 may be divided into two or more portions for every pressuregeneration chamber 12, so that only the reservoir portion 31 may be usedas a reservoir. Or, only the pressure generation chambers 12 may beprovided in the flow path forming substrate 10 and the ink supply path14 communicating with the reservoir 100 and the respective pressuregeneration chambers 12 may be provided to a member (e.g., the elasticfilm 50 or the insulator film provided as required) provided between theflow path forming substrate 10 and the protective substrate 30, forexample.

At a region facing the piezoelectric elements 300 of the protectivesubstrate 30, a piezoelectric element holding portion 32 having a spaceso as not to impede the movement of the piezoelectric elements 300 isprovided. The piezoelectric element holding portion 32 may have a spaceso as not to impede the movement of the piezoelectric elements 300 andthe space may be sealed or may not be sealed.

As such a protective substrate 30, it is preferable to use materialshaving substantially the same coefficient of thermal expansion as thatof the flow path forming substrate 10, such as glass and ceramicmaterials. In this embodiment, the protective substrate 30 is formedusing a silicon single crystal substrate which is the same material asthat of the flow path forming substrate 10.

In the protective substrate 30, a penetration hole 33 penetrating theprotective substrate 30 in the thickness direction is provided. Thevicinity of the end of the lead electrode 90 drawn from each of thepiezoelectric elements 300 is provided in such a manner as to be exposedin the penetration hole 33.

On the protective substrate 30, a drive circuit 120 for driving thepiezoelectric elements 300 arranged in parallel is fixed. As the drivecircuit 120, a circuit substrate, a semiconductor integrated circuit(IC), or the like can be used, for example. The drive circuit 120 andthe lead electrode 90 are electrically connected to each other through aconnection wiring 121 containing a conductive wire, such as a bondingwire.

Onto such a protective substrate 30, a compliance substrate 40containing a sealing film 41 and a fixing plate 42 is joined. Here, thesealing film 41 contains materials having low rigidity and flexibility.One area of the reservoir portion 31 is sealed with the sealing film 41.The fixing plate 42 is formed with a relatively hard material. A regionfacing the reservoir 100 of the fixing plate 42 is an opening portion 43completely opening in the thickness direction. Thus, one are of thereservoir 100 is sealed only by the sealing film 41 having flexibility.

In such an ink jet recording head I of this embodiment, an ink is takenfrom an ink introduction port connected to an ink supply member (notillustrated) at the outside, the inside thereof from the reservoir 100to the nozzle opening 21 is filled with the ink, and a voltage isapplied between the first electrode 60 and the second electrode 80corresponding to each of the pressure generation chambers 12 inaccordance with a record signal from the drive circuit 120 to bend anddeform the elastic film 50, the adhesion layer 56, the first electrode60, and the piezoelectric layer 70 to thereby increase the pressure ineach of the pressure generation chamber 12, whereby ink droplets aredischarged from the nozzle openings 21.

Next, one example of a method for manufacturing the ink jet recordinghead of this embodiment will be described with reference to FIGS. 5 to9. FIGS. 5 to 9 are cross sectional views in the longitudinal directionof the pressure generation chamber.

First, as illustrated in FIG. 5A, a silicon dioxide film containingsilicon dioxide (SiO₂) or the like constituting the elastic film 50 isformed on the surface of a flow path forming substrate wafer 110 whichis a silicon wafer by thermal oxidation or the like. Subsequently, asillustrated in FIG. 5B, the adhesion layer 56 containing titanium oxideor the like is formed by a reactive sputtering method, thermaloxidation, or the like, on the elastic film 50 (silicon dioxide film).

Next, as illustrated in FIG. 6A, the first electrode 60 containingplatinum, iridium, iridium oxide, or a laminate thereof is formed on theentire surface of the adhesion layer 56 by a sputtering method or thelike.

Subsequently, the piezoelectric layer 70 is laminated on the firstelectrode 60. Methods for manufacturing the piezoelectric layer 70 arenot limited. For example, the piezoelectric layer 70 can be formed by achemical solution method, such as an MOD (Metal-Organic Decomposition)method including applying a solution in which an complex is dissolvedand dispersed in a solvent and drying the same, and then firing the sameat a high temperature to thereby obtain the piezoelectric layer 70 or asol-gel method. In addition, a laser ablation method, a sputteringmethod, a pulsed laser deposition method (PLD method), a CVD method, anaerosol deposition method, and the like may be used.

A specific example of a procedure for forming the piezoelectric layer 70is as follows. First, as illustrated in FIG. 6B, a sol or an MODsolution (precursor solution) containing an complex, specifically, ancomplex containing Bi, Ce, and Fe, and La, which is blended as requiredat a target ratio is applied onto the first electrode 60 using a spincoating method or the like to thereby form the piezoelectric precursorfilm 71 (application process).

The precursor solution to be applied is obtained by mixing complexescontaining each of Bi, Ce, Fe, and La so that the molar ratio of eachmetal becomes a desired molar ratio, and then dissolving or dispersingthe mixture using an organic solvent, such as alcohol. As the complexescontaining each of Bi, Ce, Fe, and La, a metal alkoxide, an organic acidsalt, a β diketone complex, and the like can be used, for example.Examples of the complex containing Bi include 2-ethylhexanoic acidbismuth. Examples of the complex containing Fe include 2-ethylhexanoicacid iron. Examples of the complex containing Ce include 2-ethylhexanoic acid cerium. Examples of the complex containing La include2-ethyl hexanoic acid lanthanum.

Subsequently, the piezoelectric precursor film 71 is heated to a giventemperature, and is dried for a defined period of time (drying process).Next, the dried piezoelectric precursor film 71 is degreased by heatingthe same to a given temperature, and holding the same for a definedperiod of time (degreasing process). The degreasing process as usedherein refers to a process for removing the organic ingredientscontained in the piezoelectric precursor film 71 as NO₂, CO₂, H₂O, orthe like, for example. The atmosphere of the drying process or thedegreasing process is not limited and the processes may be carried outin the air or inactive gas.

Next, as illustrated in FIG. 6C, the piezoelectric precursor film 71 iscrystallized by heating the same to a given temperature, e.g., about 600to 700° C., and holding the same for a defined period of time to formthe piezoelectric film 72 (firing process). Also in the firing process,the atmosphere is not limited and the process may be carried out in theair or inactive gas.

Examples of heating devices for use in the drying process, thedegreasing process, and the firing process include an RTA (Rapid ThermalAnnealing) device that performs heating by irradiation of an infraredlamp or a hot plate.

Next, as illustrated in FIG. 7A, on the piezoelectric film 72, the firstelectrode 60 and a first layer of the piezoelectric film 72 aresimultaneously patterned using a resist having a given shape (notillustrated) as a mask so that the sides thereof incline.

Subsequently, the resist is separated, and then the application process,the drying process, and the degreasing process described above or anapplication process, a drying process, a degreasing process, and afiring process are repeated two or more times in accordance with adesired film thickness or the like to form the piezoelectric layer 70containing two or more of the piezoelectric films 72, thereby formingthe piezoelectric layer 70 containing two or more of thepiezoelectricity film 72 and having a given thickness as illustrated inFIG. 7B. For example, when the film thickness per application of thecoating solution is about 0.1 μm, the film thickness of the entirepiezoelectric layer 70 containing ten layers of the piezoelectric films72 is about 1.1 μm, for example. In this embodiment, the piezoelectricfilm 72 is provided by lamination but the piezoelectric film 72 maycontain only one layer.

After forming the piezoelectric layer 70 as described above, asillustrated in FIG. 8A, the second electrode 80 containing platinum orthe like is formed by a sputtering method or the like on thepiezoelectric layer 70, and the piezoelectric layer 70 and the secondelectrode 80 are simultaneously patterned in a region facing each of thepressure generation chambers 12, thereby forming the piezoelectricelement 300 containing the first electrode 60, the piezoelectric layer70, and the second electrode 80. The patterning of the piezoelectriclayer 70 and the second electrode 80 can be carried out at once bycarrying out by dry etching through a resist (not illustrated) formedinto a given shape. Thereafter, post-annealing may be carried out in atemperature range (600° C. to 700° C.) as required. Thus, a favorableinterface of the piezoelectric layer 70 and the first electrode 60 orthe second electrode 80 can be formed and the crystallinity of thepiezoelectric layer 70 can be improved.

Next, as illustrated in FIG. 8B, patterning is carried out for everypiezoelectric element 300 through a mask pattern (not illustrated)containing, for example, a resist or the like on the entire surface ofthe flow path forming substrate wafer 110 after the formation of thelead electrode 90 containing gold (Au), for example. Next, asillustrated in FIG. 8C, a protective substrate wafer 130 which is asilicon wafer and forms two or more protective substrates 30 is joinedthrough the adhesive 35 to the piezoelectric element 300 side of theflow path forming substrate wafer 110, and then the thickness of theflow path forming substrate wafer 110 is reduced to a given thickness.

Next, as illustrated in FIG. 9A, a mask film 52 is newly formed on theflow path forming substrate wafer 110, and is patterned into a givenshape. As illustrated in FIG. 9B, by carrying out anisotropic etching(wet etching) of the flow path forming substrate wafer 110 using analkaline solution of KOH or the like through the mask film 52, thepressure generation chamber 12, the communication portion 13, the inksupply path 14, the communication path 15, and the like corresponding tothe piezoelectric element 300 are formed.

Thereafter, unnecessary portions of the peripheral edge of the flow pathforming substrate wafer 110 and the protective substrate wafer 130 areremoved by cutting by dicing or the like, for example. Then, the maskfilm 52 on the surface opposite to the protective substrate wafer 130 ofthe flow path forming substrate wafer 110 is removed. Thereafter, thenozzle plate 20 in which the nozzle openings 21 are formed is joined andthe compliance substrate 40 is joined to the protective substrate wafer130, and then the flow path forming substrate wafer 110 or the like isdivided into one-chip size of the flow path forming substrate 10 or thelike as illustrated in FIG. 1, thereby obtaining the ink jet recordinghead I of this embodiment.

Examples

Hereinafter, the invention will be more specifically described withreference to Examples but is not limited to the following Examples.

Sample 1

First, a silicon dioxide film having a film thickness of 1070 nm wasformed on the surface of a silicon (110) substrate by thermal oxidation.Next, a titanium film was formed on the silicon dioxide film by an RFsputtering method, and was thermally oxidized to form a titanium oxidefilm having a film thickness of 40 nm. Next, a platinum film having afilm thickness of 130 nm was formed on the titanium oxide film by a DCsputtering method to be used as a first electrode oriented along (111).

Subsequently, a piezoelectric layer was formed on the first electrode bya spin coating method. The procedure is as follows. First, a xylenesolution and an octane solution of 2-ethylhexanoic acid bismuth,2-ethylhexanoic acid cerium, and 2-ethylhexanoic acid iron were mixed ata given ratio to prepare a precursor solution. The precursor solutionwas added dropwise onto the substrate on which the titanium oxide filmand the first electrode were formed, and the substrate was rotated at1500 rpm, thereby forming a piezoelectric precursor film (applicationprocess). Next, drying and degreasing were performed for 3 minutes at350° C. (drying and degreasing process). The application process and thedrying and degreasing process were repeated 3 times, and then firing wasperformed at 650° C. for 3 minutes under a nitrogen atmosphere (nitrogenflow with a flow rate of 100 cc/minute in a heating device) by RapidThermal Annealing (RTA) (firing process). By repeating, 3 times, aprocess including performing the firing process in which firing isperformed at once after repeating the application process and the dryingand degreasing process 3 times, i.e., performing the applicationprocesses nine times in total, a piezoelectric layer having a thicknessof 564 nm as a whole was formed.

Thereafter, a platinum film having a film thickness of 100 nm was formedby a DC sputtering method as a second electrode on the piezoelectriclayer, and then fired at 650° C. for 5 minutes using RTA, therebyforming the piezoelectric element 300 containing a complex oxide, whichis a perovskite type complex oxide containing bismuth, iron, and ceriumand has a molar ratio of each metal of Bi:La:Ce:Fe=(1−x−y):x:y:1 (the xand y values are as shown in Table 1), as the piezoelectric layer 70.

Samples 2 to 4

The piezoelectric element 300 was formed in the same manner as inExample 1, except changing the mixing ratios of a xylene solution and anoctane solution of 2-ethylhexanoic acid bismuth, 2-ethylhexanoic acidcerium, and 2-ethylhexanoic acid iron and using a complex oxide ofBi:La:Ce:Fe=(1−x−y):x:y:1 (the x and y values are as shown in Table 1)as the piezoelectric layer 70.

Samples 5 to 22

The piezoelectric element 300 was formed in the same manner as inExample 1, except using a mixture obtained by mixing a xylene solutionand an octane solution of 2-ethylhexanoic acid bismuth, 2-ethylhexanoicacid lanthanum, 2-ethylhexanoic acid cerium and 2-ethylhexanoic acidiron at a given ratio, repeating the firing process 4 times in whichfiring is performed at once after repeating the application process andthe drying and degreasing process 3 times, and using a complex oxide ofBi:La:Ce:Fe=(1−x−y):x:y:1 (x and y values are as shown in Table) as thepiezoelectric layer 70.

TABLE La/ 1 − x − y X Y Ce/(Ce + Bi) (Ce + Bi + La) Sample 1 0.99 0.000.01 0.01 0.00 Sample 2 0.95 0.00 0.05 0.05 0.00 Sample 3 0.90 0.00 0.100.10 0.00 Sample 4 1.00 0.00 0.00 0.00 0.00 (Comp. Ex.) Sample 5 0.940.05 0.01 0.01 0.05 Sample 6 0.90 0.05 0.05 0.05 0.05 Sample 7 0.85 0.050.10 0.11 0.05 Sample 8 0.90 0.10 0.00 0.00 0.10 (Comp. Ex.) Sample 90.89 0.10 0.01 0.01 0.10 Sample 10 0.87 0.10 0.03 0.03 0.10 Sample 110.85 0.10 0.05 0.06 0.10 Sample 12 0.83 0.10 0.07 0.08 0.10 Sample 130.80 0.10 0.10 0.11 0.10 Sample 14 0.85 0.15 0.00 0.00 0.15 (Comp. Ex.)Sample 15 0.84 0.15 0.01 0.01 0.15 Sample 16 0.82 0.15 0.03 0.04 0.15Sample 17 0.80 0.15 0.05 0.06 0.15 Sample 18 0.75 0.15 0.10 0.12 0.15Sample 19 0.79 0.20 0.01 0.01 0.20 Sample 20 0.77 0.20 0.03 0.04 0.20Sample 21 0.75 0.20 0.05 0.06 0.20 Sample 22 0.70 0.20 0.10 0.13 0.20

Test Example 1

Each of the piezoelectric elements of the samples 1 to 4 was determinedfor the relationship (P-E curve) between the polarization and electricfields by applying a triangular wave having a frequency of 1 kHz at roomtemperature using a φ=400 μm electrode pattern by “FCE-1A” manufacturedby TOYO Corp. The results of the sample 4 (Comparative Example) areillustrated in FIG. 10A, the results of the sample 1 are illustrated inFIG. 10B, the results of the sample 2 are illustrated in FIG. 10C, andthe results of the sample 3 are illustrated in FIG. 10D. As a result, asillustrated in FIGS. 10A to 10D, the samples 2 to 4 containing Bi, Fe,and Ce were ferroelectrics. In contrast, the sample 4 (ComparativeExample) which is bismuth ferrate and does not contain Ce did notexhibit a favorable hysteresis.

Test Example 2

The piezoelectric elements of the samples 1 to 4 were determined at roomtemperature for the powder X-ray diffraction pattern of thepiezoelectric layer using “D8 Discover” manufactured by Bruker AXS usinga CuKα line as the X-ray source. The X ray diffraction patterns showingthe correlation between the diffraction intensity-diffraction angle 2 θare illustrated in FIG. 11. As illustrated in FIG. 11, the peak derivedfrom the ABO₃ type structure and the peak derived from the substratewere observed in all the samples 1 to 4. In addition, as illustrated inFIG. 11, a Bi₂Fe₄O₉ hetero-phase was observed in the samples 1 to 4.

Test Example 3

Each of the piezoelectric elements of samples 1 to 4 was measured forthe J-E Curve at room temperature using “4140B” manufactured by HewlettPackard Co. The results are illustrated in FIG. 12. In addition, asillustrated in FIG. 12, the samples 1 to 3 containing Ce exhibited morefavorable insulation properties than those of the sample 4 (ComparativeExample) not containing Ce.

Test Example 4

The piezoelectric elements of the samples 1 to 3 were determined at roomtemperature for the relationship of the electric field-induceddistortion—the electric field intensity by applying a voltage having afrequency of 1 kHz using a displacement measuring device (DBLI)manufactured by aixACCT GmbH and using a θ=500 μm electrode pattern. Theresults confirmed that the samples 1 to 3 were displaced. As one exampleof the results, the results of the sample 1 are illustrated in FIG. 13.

Test Example 5

Each of the piezoelectric elements of the samples 5 to 22 was determinedfor the relationship (P-E curve) of the polarization and the electricfields in the same manner as in Test Example 1. As one example of theresults, the results of the sample 6 are illustrated in FIG. 14A, theresults of the sample 11 are illustrated in FIG. 14B, the results of thesample 17 are illustrated in FIG. 14C, and the results of the sample 21are illustrated in FIG. 14D. As illustrated in FIGS. 14A to 14D, thesamples 6 and 11 were ferroelectrics and the samples 17 and 21 wereantiferroelectrics.

Test Example 6

The piezoelectric elements of the samples 5 to 22 were determined forthe powder X-ray diffraction pattern of the piezoelectric layer at roomtemperature using “D8 Discover” manufactured by Bruker AXS and using aCuKα line as the X-ray source. As one example of the results, theresults of the sample 11 are illustrated with the results of the sample2 in FIG. 15. The results of the samples 6, 11, and 17 are illustratedin FIGS. 16A and 16B. FIG. 16B is an enlarged view of the principalportion of FIG. 16A.

As a result, the peak derived from the ABO₃ type structure and the peakderived from the substrate were observed in all the samples 5 to 22 butthe Bi₂Fe₄O₉ hetero-phase observed in the samples 1 to 4 was suppressed.

In the sample 6, the diffraction peak belonging to a phase(ferroelectric phase) exhibiting ferroelectricity was observed near20=46° as indicated by the arrow a in FIG. 16B. In the sample 17, thediffraction peak belonging to a phase (antiferroelectric phase)exhibiting antiferroelectricity was observed near 20=46.5° C. asindicated by the arrow 13 in FIG. 16B. In the sample 11, both thediffraction peak belonging to the ferroelectric phase and thediffraction peak belonging to the antiferroelectric phase were observed.This confirmed that the sample 17 was an antiferroelectric and thesamples 6 and 11 are ferroelectrics. The sample 11 exhibited theMorphotropic phase boundary (M. P. B.) of the antiferroelectric phaseand the ferroelectric phase.

FIG. 17 illustrates a diagram in which the results of analyzing each ofthe samples 1 to 22 to determine whether the samples wereantiferroelectrics or ferroelectrics and further whether or not thesamples were ferroelectrics exhibiting the Morphotropic phase boundaryfrom the X ray diffraction patterns are plotted against the compositionratio of La and Ce. As illustrated in FIG. 17, it was clarified that thepiezoelectric elements can become ferroelectrics or antiferroelectricsexhibiting an electric field-induced phase transition depending on theLa addition amount or the like.

Test Example 7

Each of the piezoelectric elements of the samples 5 to 22 was measuredfor the J-E Curve by the same method as in Test Example 3. One exampleof the results is illustrated in FIGS. 18A and 18B. FIG. 18B is adiagram in which the values at 500 kVcm⁻¹ were plotted against thecomposition ratio of Ce. The results confirmed that, even in the case ofthe piezoelectric material to which La was further added, the effects ofincreasing the insulation properties to a high degree and suppressing aleakage current obtained by the Ce addition shown in Test Example 3above can be maintained as illustrated in FIG. 18.

Test Example 8

The piezoelectric elements of the samples 5 to 22 were determined forthe relationship of the electric field-induced distortion and thevoltage at room temperature by applying a voltage having a frequency of1 kHz using a displacement measuring device (DBLI) manufactured byaixACCT GmbH and using a φ=500 μm electrode pattern. As one example ofthe results, the results of the sample 6 are illustrated in FIG. 19A,the results of the sample 11 are illustrated in FIG. 19B, the results ofthe sample 17 are illustrated in FIG. 19C, and the results of the sample21 are illustrated in FIG. 19D. In FIGS. 19A to 19D, the dotted linerepresents the polarization and the solid line represents thedisplacement. As a result, the displacement level of the sample 17 andthe sample 21 which are antiferroelectrics was high as illustrated inFIGS. 19A to 19D. The displacement of the sample 11 which exhibits theMorphotropic phase boundary was higher than that of the sample 6 whichis a ferroelectric.

Other Embodiments

As described above, one embodiment of the invention is described but thefundamental structure of the invention is not limited to theabove-described embodiments. For example, the silicon single crystalsubstrate is mentioned as an example of the flow path forming substrate10 in the embodiments described above but, without particularly beinglimited thereto, materials, such as an SOI substrate and glass, may beused.

In the embodiments described above, the piezoelectric element 300 inwhich the first electrode 60, the piezoelectric layer 70, and the secondelectrode 80 are successively laminated on the substrate (flow pathforming substrate 10) is mentioned as an example but the invention isnot particularly limited thereto and can also be applied to alongitudinal vibration type piezoelectric element in which apiezoelectric material and an electrode formation material arealternately laminated and which expands and contracts in the axialdirection.

Each of the ink jet recording heads of these embodiments constitutes apart of a recording head unit having an ink flow path communicating withan ink cartridge or the like and is mounted on the ink jet recordingdevice. FIG. 20 is a schematic view illustrating one example of the inkjet recording device.

In an ink jet recording device II illustrated in FIG. 20, cartridges 2Aand 2B constituting an ink supply member are detachably provided torecording head units 1A and 1B having the ink jet recording heads and acarriage 3 carrying the recording head units 1A and 1B is provided to acarriage axis 5 attached to a device body 4 in such a manner as tofreely move in the axial direction. The recording head units 1A and 1Bdischarge a black ink composition and a color ink composition,respectively, for example.

The carriage 3 carrying the recording head units 1A and 1B is movedalong the carriage axis 5 by transmission of a driving force of a drivemotor 6 to the carriage 3 through two or more gears (not illustrated)and a timing belt 7. A platen 8 is provided to the device body 4 alongthe carriage axis 5, so that a recording sheet S which is a recordingmedium, such as paper, which is fed by a feed roller (not illustrated)or the like, is wound around the platen 8 and conveyed.

In the embodiments described above, the description is directed to thecase where the ink jet recording head is taken as an example of theliquid ejection head. However, the invention is widely directed togeneral liquid ejection heads and it is a matter of course that theinvention can also be applied to liquid ejection heads that ejectsliquid other than ink. Examples of other liquid ejection heads includevarious kinds of recording heads for use in image recording devices,such as a printer, color material ejection heads for use inmanufacturing color filters of liquid crystal displays and the like,electrode material ejection heads for use in forming electrodes of anorganic EL display, FED (field emission display), and the like, andbioorganic material ejection heads for use in manufacturing bio chips.

The invention is not limited to the piezoelectric elements to be mountedon the liquid ejection heads typified by the ink jet recording head andcan also be applied to piezoelectric elements to be mounted on otherdevices, such as: ultrasonic devices, such as an ultrasonic transmitter,ultrasonic motors, pressure sensors, piezoelectric pumps, and vibrationpower generation devices that convert a mechanical vibration intoelectrical power. The invention can also be similarly applied topyroelectric elements, such as an IR sensor, and ferroelectric elements,such as a ferroelectric memory.

What is claimed is:
 1. A piezoelectric element, comprising: apiezoelectric layer between electrodes, wherein the piezoelectric layeris a ABO₃ perovskite type complex oxide containing bismuth, iron, andcerium, the cerium exists in the A site, and the piezoelectric layercontains the cerium in a proportion of 0.01 molar ratio or more and 0.13molar ratio or lower based on the total amount of the bismuth and thecerium.
 2. The piezoelectric element according to claim 1, wherein thepiezoelectric layer further contains lanthanum.
 3. The piezoelectricelement according to claim 2, wherein the piezoelectric layer containsthe lanthanum in a proportion of 0.05 molar ratio or more and 0.20 molarratio or lower based on the total amount of the bismuth, the cerium, andthe lanthanum.
 4. The piezoelectric element according to claim 2,wherein the piezoelectric layer exhibits an electric field-induced phasetransition.
 5. The piezoelectric element according to claim 2, whereinthe piezoelectric layer is a ferroelectric.
 6. The piezoelectric elementaccording to claim 1, wherein, in the piezoelectric layer, a diffractionpeak belonging to a phase exhibiting ferroelectricity and a diffractionpeak belonging to a phase exhibiting antiferroelectricity aresimultaneously observed in a powder X-ray diffraction pattern.
 7. Aliquid ejection device, comprising the piezoelectric element accordingto claim
 1. 8. An IR sensor, comprising the piezoelectric elementaccording to claim
 1. 9. An ultrasonic device, comprising thepiezoelectric element according to claim 1.